(1) Field of the Invention
This invention relates to a circuit for triggering a strobe light or other appropriate source of illumination located between two underwater break screens.
(2) Description of the Prior Art
The Adaptable High Speed Underwater Munition (AHSUM) project needed a method to obtain photographs of underwater projectiles during the course of their test series. Prior to this time, there was no satisfactory means of obtaining the photographs that were needed, nor was there a device applicable to a variety of conditions.
The following patents, for example, disclose various types of photography, including underwater photography and circuits in connection therewith, but do not disclose a device for controlling an underwater strobe light for the purpose of taking underwater photographs of a high speed projectile.
U.S. Pat. No. 3,690,233 to Billingsley;
U.S. Pat. No. 4,418,999 to Baxter;
U.S. Pat. No. 4,878,074 to Peng; and
U.S. Pat. No. 5,581,078 to Sears.
Specifically, the patent to Billingsley discloses a detecting means responsive to a passing car to produce an indicating signal. A camera and a flash lighting unit positioned down the road from the detecting means are activated simultaneously to illuminate and photograph the oncoming car. The illumination lies primarily in a spectrum including the visible deep red, the near infra-red and the intermediate infra-red. Only the visible deep red and the near infra-red radiations are able to penetrate the infra-red filtering windshield and then reflect back to the camera through an optical filter which passes only said visible deep red, near the infra-red and the small amount of intermediate infra-red radiations that pass back through the windshield. Thus the glare from ambient light is eliminated. A film sensitized to the visible deep red and to the near infra-red radiations is employed in the camera. The aforementioned system provides a photograph of the driver""s facial features either during the day or at night and without causing impairment of his vision.
The patent to Baxter discloses a synchronizing circuit which enables a desired phenomena to occur, such as the discharge of a flash illuminating means at a precise point along the path of travel of an article irrespective of the speed of the article in that path. The circuit utilizes two spaced sensors upstream of the precise point. The sensors are operable to detect the passage of the article and each sensor is connected to the respective counter. When the sensor detects the passage of the article, it starts its respective counter counting in one direction at one particular counting rate. When the second sensor detects the passage of the article, it causes its respective counter to count in the opposite direction from the value of the count in the first count at a different but faster counting rate. The circuit includes gate means which determine when the count has returned to a predetermined count to then cause said phenomena to occur.
Slaght et al. discloses a system and method for determining the relative velocities of a projectile at different portions of its path in which a plurality of signaling detector stations are arranged at predetermined intervals along such path. A common receiving station is arranged to receive signals from the detector stations through a common communication channel and has a memory unit capable of storing pulses corresponding to the signals received, and a calculator capable of analyzing adjacent pairs of the pulses which have been produced by passage of the projectile over two or more of the path intervals monitored by the detector stations to determine the relative velocities of the projectile as it traverses the path intervals monitored by different pairs of detector stations. This information is used to study retardation properties of a projectile.
Peng discloses a dynamic particulate observation apparatus for monitoring a moving particle including a black box having an internal space enclosed therewithin, which shields the space form the infiltration of light outside; means for generating particles moving across the black box; means for emitting a flash of light within the black box at a predetermined frequency; and means for taking down the images of the particles generated by the generating means when the emitting means emits flashlights. The dynamic particulate observation apparatus according to the invention is cheap and easy to assemble, and renders all the necessary functions of a conventional dynamic particulate observation apparatus.
The patent to Sears discloses a ballistic optical camera trigger having an integrated circuit capable of converting light to a proportional frequency, wherein the integrated circuit has a fast response time and a wide dynamic range which allows it to sense positive or negative changes in light fast enough to trigger without delay for high speed imaging without computational delays or jitter causing interference. The frequency output of the integrated circuit is tracked by a phase lock loop/voltage controlled oscillator to allow it to follow slow changes in light, but not fast changes in light caused by, for example, a projectile such a as a bullet. The frequency output from the integrated circuit is provided to one input of a logic gate which receives at another input thereof, a shaped pulse from the phase lock loop/voltage controlled oscillator circuit, wherein the output of the logic gate is applied to a one-shot for outputting a trigger signal.
It should be understood that the present invention would in fact enhance the functionality of the above patents by providing a control device for an underwater strobe light for the purpose of taking underwater photographs, particularly in a test environment.
Therefore it is an object of this invention to provide a device for controlling a source of illumination in underwater photography.
Another object of this invention is to provide a device for controlling a strobe light in underwater high speed photography.
Still another object of this invention is to provide a device for controlling a strobe light in underwater high speed photography, the device including a novel control circuitry.
A still further object of the invention is to provide a circuitry which is an accurate and inexpensive method to control a timed illumination of a strobe light in underwater high speed photography.
Yet another object of this invention is to provide a device and circuitry for controlling a strobe light in underwater high speed photography which is simple to manufacture and easy to use.
In accordance with one aspect of this invention, there is provided a device for controlling a strobe light in underwater high speed photography. The device includes a plurality of spaced break screen members or sensing coils, a projectile for launch through the series of break screen members, a camera having a shutter opened at a predetermined timing prior to release of the projectile and closing at a predetermined timing subsequent to release of the projectile, and a strobe light opposed to the camera for illumination at a time when the projectile passes in front of the camera. A trigger device is positioned on the break screen member positioned immediately uprange of the camera. With a time delay programmed into a Programmable Array Logic (PAL), a control circuitry receives the trigger information and creates a timed signal to control the illumination of the strobe light.
In accordance with another aspect of this invention, the control circuitry includes a first D flip-flop for receiving a signal output from a break screen upon passing of a projectile therethrough, the first D flip-flop additionally having a constant voltage applied to its D-input and a resulting latched output signal. An AND gate receives an output signal of the first D flip-flop, the AND gate additionally having a CRYSTAL_IN signal applied thereto for maintaining a stable clock to counters of the PAL, and a resulting output signal only when the latched output signal from the first D flip-flop is high. An N-bit counter receives the output signal of the AND gate, the N-bit counter outputting delay generation logic upon lapse of a predetermined length of time. A second D flip-flop receives the delay logic signal, and additionally has a constant voltage applied to it""s D input and a resulting latched output signal, wherein a rising edge of an output generated by the second D flip-flop identifies a beginning of a camera activation window. A second AND gate receives the output signal of the second D flip-flop, the second AND gate additionally receives a CRYSTAL_IN signal applied thereto for maintaining a stable clock to counters of the PAL, and a resulting output signal is provided by the second D flip-flop. A second independent N-bit counter outputs a count. A second delay generation logic block receives the output of the second N-bit counter, and outputs a high pulse signal upon lapse of a predetermined count. A third D flip-flop receives the output pulse signal from the second delay generation logic, and additionally has a constant voltage applied to it""s D input and a resulting latched output signal, wherein a rising edge of an output generated by the third D flip-flop identifies an end of the camera activation window. An exclusive OR gate receives outputs from each of the second D flip-flop and the third D flip-flop, the exclusive OR gate producing a high pulse from the time delayed trig out goes high to the time second delay goes high, an output of the exclusive OR gate passing through an inverter to generate the desired low pulse. This output signal is buffered via a separate non-inverting buffer (whose open collector is pulled up to 5 VDC) and then sent to the strobe light trigger.
Illumination is controlled by the control circuitry at the exact moment the projectile passes the lens of the camera.